1. Field of the Invention
The present invention relates to an image-forming apparatus with an automatic-document feeder which has a document-transporting belt for transporting an original during contacting each other.
2. Description of the Related Art
Recently, an automatic-document feeder used with an image-forming apparatus such as on a plain paper copying machine, as, for example, disclosed in Japanese Patent Publication (Kokai) No. 4-23752, has had a document-transporting belt for transporting an original onto a platen of the image-forming apparatus and for positioning it. The document-transporting belt, generally, is made from a high-friction material, and transports an original by its frictional force. Thus, if an opposite surface of an original which contacts the document-transporting belt has an image, the document-transporting belt gets dirty easily. Moreover, it is necessary to utilize a resource effectively in consideration of an environmental problem, as a result, an original which has an image on two-sides is increasing. When the original transported has an image on two-sides and both the surfaces are set on the platen continuously, the images of both the surfaces may attach to the document-transporting belt because both the surfaces contact the document-transporting belt. Therefore, the document-transporting belt gets dirty more easily.
Such a dirty document-transporting belt makes a copy image formed on an image-bearing material, e.g., a paper sheet dirty in many cases. For example, when the paper sheet is bigger than the original, and an original image reduced is smaller than the paper sheet, the copy image of the dirty document-transporting belt is formed in the circumference of the paper sheet. If an original is a sheet of tracing paper which is a high transmittance sheet, the copy image of the dirty document-transporting belt is formed through the original.
For these reasons, a document-transporting belt has to be cleaned frequently and has to be renewed if a document-transporting belt is too dirty.